Furthermore, a steep-gradient approach can make it necessary to use airbrakes and/or spoilers, which increase the approach speed. In such a situation, the aircraft must decelerate between the steep-gradient segment and the threshold of the strip. In practice, the greater the speed is when the wheels touch down, the greater is the length needed to perform the landing. Now, the length of a strip that can be used for the landing is predetermined and limited. In the case of manual piloting, the pilot must therefore, in such a situation, have the aircraft decelerate by successive breaks of the gradient, while progressively retracting the airbrakes and/or the spoilers manually. These breaks of gradient constitute a succession of rectilinear segments, each time presenting a constant pitch-down gradient, gradients that progressively decrease until the landing, that is, until a final gradient normally of the order of 3′. It is therefore necessary, in such a situation, to provide the pilot with the appropriate information enabling him to correctly perform this difficult maneuver.
Moreover, in a flight at low altitude along a flight path consisting of a succession of rectilinear segments with constant pitch-down or pull-up gradients, in particular when the flight is performed by following a flight director system, the pilot needs to anticipate the various changes of gradient, in order to follow the flight path as effectively as possible, and therefore to keep a sufficient safety margin relative to the ground. In such a situation, there is also an interest in being able to provide the pilot with appropriate information, enabling him to follow the path as effectively as possible.
The present invention relates to a method for assisting in the piloting of an aircraft in a flight along a flight path comprising a plurality of successive rectilinear segments, which makes it possible to provide the pilot of the aircraft with the information needed to pilot said aircraft in said flight.
To this end, according to the invention, said method, whereby there is presented, on a display screen of a head-up display device, superimposed on the environment seen at the front of the aircraft and in conformal projection, a gradient scale and, on this gradient scale, a gradient symbol illustrating the current gradient of the aircraft, is noteworthy in that the following series of successive steps is carried out automatically and repetitively:    a) the respective gradients of a plurality of successive rectilinear segments of said flight path are determined, as is change information that makes it possible to determine changes of gradient (that is, changes of rectilinear segment);    b) from said gradients and from said change information, for each of said rectilinear segments, a characteristic angle is determined which represents the gradient angle by which the corresponding rectilinear segment is seen by the pilot of the aircraft, from the current position of said aircraft, and    c) there are presented, on said display screen of the head-up display device, superimposed on the environment seen at the front of the aircraft and in conformal projection, characteristic signs which respectively depend on said characteristic angles and which are positioned on the gradient scale so as to display differences in gradient relative to said gradient symbol (illustrating the current ground gradient), each duly displayed difference in gradient presenting on the gradient scale a gradient that is equal to the corresponding characteristic angle determined in the step b).